Telephone system.



PATENTED JUNE 28, 1904.

w. M. DAVIS. TELEPHONE SYSTEM.

APPLIOATION FILED MAR. 2, 1903.

N0 MODEL.

Inv enTur "Willla WiTIlEEEEE:

M. Davis,

ZAEEIFIIEH r Nsams No. 763,374. Patented June 28, 1904.

UNITED STATES PATENT FFICE.

WVILLIAM M. DAVIS, OF CHICAGO, ILLINOIS, ASSIGNOR TO THE STROMBERG- CARLSON TELEPHONE MANUFACTURING COMPANY, OF ROCHESTER, NEIV YORK, A CORPORATION OF NEW YORK,

TELEPHONE SYSTEM.

SPECIFICATION forming part of Letters Patent No. 763,3 74, dated June 28, 1904. Application filed March 2, 1903. Serial No. 145,848. No model.)

To all whom it may concern: denser 5. hen in its upper position, due

Beit known thatLWILLIAMM. DAVIS, a citito the removal of the weight of the receiver 5 zen of the United States, residing at Chicago, 6, the switch-hook closes a circuit between in the county of Cook and State of Illinois, have the line-limbs through a transmitter 7 and a invented acertain new and useful Improvement primary coil 8 of an induction-coil whose secin Telephone Systems, of which the following ondary winding 9 is connected with the reis a full, clear, concise, and exact description, ceiver 6. 5% reference beinghad to the accompanying draw- There are provided at the central exchange ings, forming a part of this specification. C a pair of bus conductors l0 and 11, to which 10 My invention relates to telephone systems, may be connected, by means of the switch 12, and more particularly to telephone systems either the battery 13 or the battery 1A. 1 in which the current for the substation-transhave shown the negative terminals of both of mitters is supplied by a battery or source of these batteries permanently connected with current located at the central exchange. It the bus conductor 10. The switch 12 is shown I 5 has heretofore been one of the disadvantages in the position to connect the positive pole of of such telephone systems that the means emthe battery 13 with the bus-bar 11. hen ployed for testing the condition of a line to thrown in its alternate position, the switch ascertain whether or not such line is in use connects the positive pole of the battery 14 has caused a disagreeable click in the subwith the bus-bar 11. A second set of con- 2 scribers receiver. It is the principal object tacts 15 is provided for a purpose to be hereof my invention to provide testing means inafter more fully explained. The limb 2 of which shall avoid this disagreeable click. As the telephone-line leads to the bus-bar 11. is well known by those'skilled in the art, it is The limb 3 of the telephone-line leads through common practice to provide for the source of contacts of the calling spring-jack 16 and the 25 current at the substation two storage batanswering spring-jack 17 through the line-reteries, either one of which alone is usually lay 18 to the bus-bar 10. employed to supply current for talking and A local circuit containing the line-signal signaling purposes. It is the practice to in the form of an incandescent lamp 19 is charge, by means of a suitable generator, the controlled by the armature 20 of the line-re- 3 battery which is not being utilized for the lay. The tip-springs 21 of themultiple springpurpose of supplying current for the operajacks are permanently connected with the limb tion of the system. It is the purpose of my 2 of the telephone-line; The sleeve-springs 8O invention to employ this idle battery for the 22 and contacts 23 form a serial path for the operation of the testing means employed. line-limb 3 through the multiple jacks asso- 35 The testing-circuit of my invention is sepaciated therewith. Each of the spring-jacks is rate and distinct from the line or signaling provided with a test-thimble 24?, the test-thimcircuit, whereby the currents used in affordbles for the multiple jacks associated with any 8 5 ing the busy-test signal do not affect the subone line being connected together, asshown. station-receivers to produce the disagreeable The operators cord-circuit comprises the 4 click hereinbefore referred to. usual answering-plug 25 and the calling-plug My invention will be more clearly under- 26, the tip-contacts of which are connected stood by reference to the accompanyingdrawthrough a tip-strand 27 and the sleeve-con- 9 ing, in which is shown at each of the subtacts of which are connected throughasleevestations A and B the usual substation apparastrand 28. The usual ringing and listening 45 tus, comprising a switch-hook 1, which when key 29 is provided, which when actuated in in its lower depressed condition closes a cirone direction serves to connect the operators cuit between the line-limbs 2 and 3 through telephone set 30 in bridge of the cord-circuit the call-bell L and the serially-connected conand which when operated in the reverse direction serves to connect the ringing-generator 31 with the cord-strands leading to the calling-plug 26. The sleeve-strand includes within its circuit the supervisory relays 32 and 33, respectively bridged by the condensers 34 and 35. A conductor including the impedance-coil 36 leads from the common terminal of the supervisory relays to the busbar 10. The armatures 37 and 38 of the supervisory relays serve when in their unattracted condition to close circuit through the associated supervisory signal-lamps 39 and 40 when the associated plug of the calling-circuit is inserted within a line-jack. A condenser 41 is included in the tip-strand, as shown, this condenser being shunted, however, by the conductor 42, which leads to contact 43, normally connected with the tip-spring of the listening-key. A test-winding 44 is inductively related to the induction-coil of the operators telephone set, the battery-circuit through this test-winding being controlled by the armature 45 of test-relay 46. This testrelay is included in a circuit between the contact 47 and the switch-contacts 15, associated with the switch 12, a resistance 48 being included in the circuit. It will be seen that in the position shown the switch 12 connects the positive pole of the battery 14 with the conductor leading to the test-relay 46. The reversal of the switch 12 causes a connection of the positive pole of the battery 13 with the conductor leading to the test-relay 46.

It is common practice in the telephone art to employ in central-energy systems two storage batteries, one of which is preferably connected with the telephonic apparatus, while the other is either idle or being charged by a suitable charging-generator. Thus the accompanying drawing shows the battery 13 connected with the telephone system to supply talking and signaling currents, while the battery 14 may be considered as idle or as connected with a charging-generator. The reversal of the switch 12 serves to reverse the connections of the batteries 13 and 14. V

The operation of my system may be described as follows: A subscriber at substation A upon removing his receiver from its hook causes the closure of a circuit through the line-relay 18, whereupon the same is energized to cause the attraction of the armature 20, which closes circuit through the line-signal19, thereby notifying the operator that the subscriber at substation A desires connection. The operator thereupon inserts the answering-plug 25 of her cord connecting apparatus within the answering-jack 17, thereby breaking the contact between the sleevespring 22 and the jack-contact 23, thereby interrupting the continuity of the circuit through the line-relay 18. The consequent dcenergization of the line-relay 18 permits the retraction of the armature 20, thereby opening the circuit through the line-signal 19 to cause its extinction. The operator manipulates her listening-key to connect her telephone set in bridge of the cord-circuit and ascertains the number of the desired connection. It will be seen that the insertion of the operators answering-plug 25 within the jack of the calling subscriber closes a circuit through the supervisory relay 32, whereby the same is energized to cause the attraction of its armature 37 and the extinction of the lamp 39, which otherwise would have been illuminated upon the insertion of the plug within the jack. Upon ascertaining that the subscriber at substation B is desired the operator inserts her callingplug within a multiple line-jack 16 and thereupon manipulates her ringing-key to connect the generator 31 in bridge of the cord strands connected with the line to substation B. The subscriber at substation B upon answering the calling-signal removes his receiver from its book, thereby closing circuit through the supervisory relay 33, which attracts its armature 38 to interrupt the flow of current previously established through the line-lamp 40. The replacement of the telephone-receivers upon their hooks when the conversation has been finished causes the deenergization of the supervisory relays 32 or 33 to release the armatures 37 or 38, whereby a circuit is completed through the associated supervisory lamp 39 or 40 to cause its illumination. The operator perceiving the disconnect-signal rcmoves the plugs of her cord-circuit from the line-jacks. whereupon the line instrumentalities are restored to their normal condition.

The means for testing the condition of a called line in order to ascertain whether or not such line isin use is as follows: It will be seen that the negative pole of the idle battery is permanently connected with the bus-bar 10. with which the sleeve-contacts of the plugs of the cord-circuit are permanently connected through the supervisory relays and the impedance-coil 36. within a line-jack raises the potential of the test-thimble to that of the negative pole of the idle battery. The manipulation of the listening-key 29 connects the tip-strand leading to the calling-plug through the test-relay 46, the resistance 48, a switch-contact 15, and switch 12 to the positive pole of the idle battery 14. Thus the application of the tip-contact of a calling-plug 26 to a test-thimble of a line with which other cord connecting apparatus is connected causes the closure of a circuit through the idle battery 14 and the test-relay 46. The energization of the testrelay causes the attraction of its armature 45 to close a circuit through the test-winding 44, which produces a click in the operators telephone-receiver to notify her of the busy condition of the, tested line.

It will be seen that I have provided a testcircuit and means for supplying test-current entirely independent of the means and cir- Thus the insertion of a plug,

cuits employed for the operation of the signaling and talking instrumentalities of the system.

My invention provides a further improvement in the fact that the test-circuit employs for its energizing-currents the idle set of storage batteries which is not connected with the signaling or talking circuits of the system.

While I have herein shown and described one particular embodiment of my invention, it will be apparent that many modifications therein may be employed Without departing from the spirit of my invention. I do not, therefore, wish to limit myself to the precise disclosure herein set forth; but, Having described my invention, I claim as new and desire to secure by Letters Patent 1; ,Inatelephone-exchangesystem, the combination with a telephone-line extending by its limbs from a substation to an exchange,

of a common source of current at the exchange for supplying talking and signaling currents to said line, multiple springacks associated with said line, test-thimbles for said springjacks, cord connecting apparatus for connecting said line with another for conversation, a test-contact associated with said cord connecting apparatus, an auxiliary source of current, and a test-relay adapted when testing to be energized by said auxiliary source of current to close a local circuit through a test-winding and said common source of current.

- 2. In'atelephonerexchangesystem,thecom bin'ation with a telephone-line extending by its limbs from a substation to an exchange, of a common so urce of current at the exchange for supplying talking and signaling currents to said line, multiple spring-jacks associated with said line, test-thimbles for said springjacks, cord connecting apparatus for connecting said line with another for conversation, a test-contact associated with said cord connecting apparatus, an auxiliary source of. current, a test-relay, and means whereby the application of said test-contact to one of said testthimbles when saidline is busy causes the closure of a circuit through said test-relay and said'auxiliary source of current.

3. In a telephone-exchange system, the comwith said line, test-thimbles for said spring-' jacks, cord connecting apparatus for connecting said line with another for conversation, a

test-contact associated with said cord connecting apparatus, an auxiliary source of current,

a test-relay, atest-winding inductively associated with the operators telephone set, a local circuit for said test-winding controlled by said test-relay, and means whereby the application of said test-contact to one of said testthimblcs when said line is busy causes the 1 for supplying talking and signaling currents to said line, multiple spring-jacks associated with said line, test-thimbles for said springjac'ks, cord connecting apparatus for connecting said line with another for conversation, a test-contact associated with said cord connecting apparatus, an auxiliary source of current having one pole connected with the sleeve- 'strand leading toa sleeve-contact of a connecting-plug of the cord connecting apparatus, and the other pole connected with the test-contact of the cord connecting apparatus when testing, signaling apparatus adapted to be actuated by an electric current, and means 'whereby the application of said test-contact to one of said test-thi mbles when said line is busy causes the'closure of a circuit through said signaling apparatus and said auxiliary source of current.

5. In a teleph one-exchange'system, the combination with a telephone-line extending by its limbs from'a substation to an exchange,

of a common'source of current at the exchange for supplying talking and signaling currents to said line, multiple spring-jacks associated with said line, test-thimbles for said springjacks, cord connecting apparatus for connecting said line with another for conversation, a

test-contact associated with said cord ,connect-' ing apparatus, and an auxiliary source of currenthaving one pole connected with the sleevestrand leading to a sleeve-contact of a connecting-plug or the cord connecting apparatus and the other pole connected through a test-relay with the test-contact of the cord connecting apparatus when testing, whereby the application of said test-contact to one of .said test-thin]- bles when said line is connected With other duplicate cord connecting apparatus causes the closure of a circuit through said test-relay and said auxiliary source of current.

6. In atelephone-exchange system, the combination with a telephone-line extending by its limbs from a substation to an exchange,

of a common source of current at the exchange for supplying talking and signaling currents to said" line, multiple spring-jacks associated with said line, test-thimbles for said springjacks, cord connecting'apparatus' for connect ing said line with another for conversation, a'

test-contact associated with said cord connecting apparatus, an auxiliary source of current having one pole connected with the sleevestrand leading to a sleeve-contact of a connecting-plug of the cord connecting apparatus and the other pole connected through a test-relay with the test-contact of the cord connecting apparatus when testing, whereby the application of said test-contact to one of said testthimbles when said line' is connected with other duplicate cord connecting apparatus causes the closure of a circuit throughsaid test-relay and said auxiliary source of current, a test-winding inductively associated with the operators telephone set, and a local circuit for said test-winding controlled by said test-relay.

7. In a telephone-exchange system, the combination with a telephone-line extending by its limbs from a substation to an exchange, of a common battery at the exchange for supplying talking and signaling currents to said line, a second relay-battery adapted to be used alternately with said first battery for supplying talking and signaling currents to said line, multiple spring-jacks associated with said line, test-thimbles for said spring-jacks, duplicate cord connecting apparatus for connecting said line with another for conversation, a test-contact associated with each of said cord connecting apparatus, signaling apparatus adapted to be actuated by an electric current, and means whereby the application of a test-contact of one of said cord connecting apparatus to one of said test-thimbles when said line is connected with another cord connecting appara tus causes the closure of a circuit through said signaling apparatus and said second battery.

8. In a telephone-exchange system, the combination with a telephone-line extending by its limbs from a substation to an exchange, of a common battery at the exchange for supplying talking and signaling currents to said line, a second relay-battery adapted to be used alternately with said first battery for supplying talking and signaling currents to said line, multiple spring-jacks associated with said line, test-thimbles for said spring-jacks, duplicate cord connecting apparatus for connecting said line with another for conversation, a test-contact associated with each of said cord connecting apparatus, a test-relay, a test-winding inductively associated with the operators telephone set, a local circuit for said test-winding controlled by said test-relay,and means whereby the application of a test-contact of one of said cord connecting apparatus to one of said test-thimbles when said line is connected with another of said cord connecting apparatus causes the closure of a circuit through said test-relay and said second battery.

9. In a telephone-exchange system, the combination with a telephone-line extending by its limbs from a substation to an exchange, of a common battery at the exchange for supplying talking and signaling currents to said line, a second relay-battery adapted to be used alternately with said first battery for supplying talking and signaling currents to said line, multiple spring-jacks associated with said line, test-thimblcs for said spring-jacks, duplicate cord connecting apparatus for connecting said line with another for conversation, a test-contact associated with each of said cord connecting apparatus, a test-relay, and means whereby the application of a test-contact of one of said cord connecting apparatus to oneof said testthimbles when said line is connected with another of said cord connecting apparatus causes the closure of a circuit through said test-relay and said second battery. 7

10. In a telephone exchange system, the combination with a telephone-line extending by its limbs from a substation to an exchange, of a common battery at the exchange for supplying talking and signaling currents to said line, a second relay-battery adapted to be used alternately with said first battery for supplying talking and signaling currents to said line,

multiple spring-jacks associated with said line, test-thimbles for said spring-jacks, duplicate cord connecting apparatus for connecting said line with another for conversation, a testcontact associated with each of said cord connecting apparatus, and a test-relay adapted when testing to be energized by said relaybattery to close a local circuit including a testwinding and said common battery.

11. In a telephone-exchange system, the

combination with a telephone-line extending other for conversation, a test-contact associated with each of said cord connecting apparatus, a test-circuit, and means whereby either of said batteries may be connected with the telephone-line and cord connecting apparatus while the other of said batteries is connected with the test-circuit.

12. In a telephone-exchange system, the combination with a telephone-line extending by its limbs from a substation to an exchange, of a common battery at the exchange for supplying talking and signaling currents to said line, a second relay-battery adapted to supply talking and signaling currents to said line in place of said first battery, multiple springjacks associated with said line, test-thimbles for said spring-jacks, duplicate cord connecting apparatus for connecting said line with another for conversation, at test-contact associf of a common battery at the exchange for supplying talking and signaling currents to said line, asecond relay-battery adapted to supply talking and signaling currents to said line in place of said first battery, multiple springjacks associated with said line, test-thimbles for said spring-jacks, duplicate cord connecting apparatus for connecting said line with another for conversation, a test-contact associated with each of said cord connecting apparatus, a test-circuit, and means whereby either of said batteries may be connected with the telephone-line and said cord connecting apparatus while one pole of the other of said batteries is connected with the sleevestrands leading to the sleeve-contacts of the connecting-plugs of said cord connecting apparatus and the other pole is connected with the testcontact of a cord connecting apparatus when testing, whereby the application of said testcontact to one of said test-thimbles when said line is connected with another of said cord connecting apparatus causes the flow of current through said test-circuit.

l4. In a telephone-exchange system, the combination with a telephone-line extending I adapted to supply talking and signaling currents to said line, multiple spring-jacks associated with said line, test-thimbles for said spring-jacks, duplicate cord connecting apparatus for connecting said line with another for conversation, atest-contact associated with each of said cord connecting apparatus, switching means adapted to connect either of said batteries with the line and cord circuits and to connect the other battery with a test-circuit, one pole of said second battery being connected to the sleeve-strands of said cord-circuit and the other pole of said battery being connected through a test-relay with the testcontact of a testing cord connecting apparatus when testing, and a signal-receiving means controlled by'said test-relay.

In witness whereofl hereunto subscribe my name this 20th day of February, A. D. 1903.

WILLIAM M. DAVIS.

- Witnesses:

HARVEY L. HANsoN, JOHN STAHR. 

